Downhole corrosion inhibition is extremely important in the production of oil and gas. Produced fluids are generally a mixture of liquid petroleum, natural gas, and formation water, and generally further include one or more corrodents, such as hydrogen sulfide, carbon dioxide, dissolved oxygen, and the like. Corrosion inhibitors employed for downhole applications are generally organic film formers that act by filming the downhole metal surfaces and persist as a film at least some period of time after the inhibitor feed is discontinued. Such a persistent film-forming corrosion inhibitor is commonly introduced downhole by using a treating truck to pump the inhibitor down the tubing or into the annulus of the well, followed by an overflush of fluid, which flushing fluid is generally produced water.
Such film-forming organic corrosion inhibitors are useful in producing wells where the fluid in contact with the metal surfaces to be protected is generally a mixture of hydrocarbons, usually crude oil, and brine, with the hydrocarbons constituting at least a significant, if not predominant, phase of the fluid. The corrosion inhibitors generally film the metal surfaces from the hydrocarbon or oil phase and hence the corrosion inhibitor should generally be oil soluble and only water dispersible. The persistent nature desired in the films of such inhibitors permit intermittent applications of such inhibitors in oil or gas wells, such as the truck treatment mentioned above, or periodic batch treatments, or other treatments where the inhibitor is not applied on a continuous basis. Intermittent treatments of persistent corrosion inhibitors generally employ less inhibitor than, for instance, continuous treatment of water soluble or dispersible inhibitors commonly used in wells having water as the predominant phase, for instance injection water wells.
Such oil soluble, water dispersable organic film forming corrosion inhibitors are conventionally commercially supplied as a composition containing the corrosion inhibitor actives, that is the agent(s) providing corrosion inhibition activity, a surfactant, and a solvent. The surfactant is used to disperse the corrosion inhibitor in the brine so that it migrates down the hole to the site of use. The solvent often used is a mixture of aromatic hydrocarbons, which are both relatively expensive and require special handling techniques when the composition is being shipped. The expense of the surfactant, the solvent, and the special handling requirements all contribute to the expense of a corrosion inhibition program.
It is desirable to provide a corrosion inhibitor composition that provides not only advantageous film persistency but also advantageously effective filming from the production fluid onto the metal surfaces. It is desirable to provide a corrosion inhibitor that provides a high degree of downhole corrosion inhibition. It is desirable to provide a corrosion inhibitor that reduces the oil/water handling problems in the application of the corrosion inhibitor. It is desirable to provide a corrosion inhibitor that requires a lesser volume of flushing fluid. It is desirable to provide a corrosion inhibitor composition that is more efficiently carried to the downhole site of use. These and other advantages are provided by the present invention as disclosed and discussed in more detail below.